Mobile communication is constantly making progress. Under one aspect of such progress, devices such as terminals are capable to communicate using more than one radio access technology RAT. Hence, in each such multi-RAT enabled device, plural RAT's and corresponding RAT communication units coexist. In view of such co-existence, in-device interference may occur and be detrimental to the device's performance.
General technical details of such scenarios, e.g. under LTE™ and coexisting other RAT's, such as ISM as an example only, and adopted communication protocols are publicly available. A repeated detailed description of each such property/functionality of the known LTE™ system is considered dispensable as those skilled in the pertinent art of technology will readily understand the description as given herein. Examples of the present invention exploit those basic properties and at least in aspects modify the functionality so as to obtain the advantages of at least some embodiments of the present invention.
Those devices in such multi-RAT scenarios comprise network transceiver devices or, more general, network entities eNB and terminals UE. A typical example, when applying LTE™ terminology, of such network entities reside in general in evolved NodeBs (eNB's), such as a macro eNB (of “large” coverage) and pico or femto eNBs. Terminals such as user equipments UE are present within the coverage of such entities. Further, a terminal may communicate with another entity such as an access point AP of another RAT, e.g. a WiFI™/ISM AP.
Thus, as described, in order to allow users to access various networks and services ubiquitously, an increasing number of UEs are equipped with multiple radio transceivers. For example, a UE may be equipped with LTE, WiFi, and Bluetooth transceivers, and GNSS receivers. One resulting challenge lies in trying to avoid coexistence interference between those collocated radio transceivers. FIG. 5 shows an example of coexistence interference for three RAT's: LTE, GPS (example of GNSS), WiFI™ in terms of the baseband parts, the radio frequency RF parts and schematically the antennas thereof, as well as potential interference between some pairs of RAT.
Due to extreme proximity of multiple radio transceivers within the same UE, the transmit power of one transmitter may be much higher than the received power level of another receiver. By means of filter technologies and sufficient frequency separation, the transmit signal may not result in significant interference. But for some coexistence scenarios, e.g. different radio technologies within the same UE operating on adjacent frequencies, current state-of-the-art filter technology might not provide sufficient rejection. Therefore, solving the interference problem by a single generic RF design may not always be possible and alternative methods need to be considered. There is an ongoing work item in standardization bodies on this topic. Also, typically, there are four proposed usage scenarios:
1a) LTE+BT earphone (VoIP service)
1b) LTE+BT earphone (Multimedia service)
2) LTE+WiFi portable router
3) LTE+WiFi offload
4) LTE+GNSS Receiver
Also, quite a few solutions are proposed to solve this potential interference, including TDM solution, FDM solution, and autonomous denial.
Autonomous denial is a good approach to remove the in-device interference for short-rare but critical WiFi/BT signaling. However, there are many concerns on the autonomous denial's negative impact in LTE system performance. For example, the eNB might interpret such autonomous denial as PDCCH failure, and might impact on PDCCH aggregation level, or wrong link adaptation, and eventually impact LTE system capacity. So, some proposals suggest setting a prohibition mechanism for LTE autonomous denial.
Two main approaches to restrict autonomous denials are:
1) setting a prohibit timer,
2) setting an autonomous denial rate.
For approach 1, after a UE performs autonomous denial, the prohibit timer starts to run, and it is not allowed to perform another (subsequent) autonomous denial until the prohibit timer expires.
For approach 2, a UE is only allowed to perform a limited number of autonomous denials during a certain period.
Note that when the period for both approaches is the same and the number of denials for approach 2 is set to 1, then the approaches are the same, thus, approach 1 is a borderline case of approach 2.
However, both approaches have a certain drawback as they can't deal with the unexpected significant ISM signaling.
For example, for approach 1, after UE performs LTE autonomous denial, the prohibit timer starts to run. But while the prohibit timer is running, another unexpected significant ISM signaling needs to be received. But according to the rule, UE can't receive it during the remaining period, because using autonomous denial of an LTE UL transmission is not possible, and then this significant ISM signaling will be missing which may cause big performance loss on ISM side, such as connection loss.
For approach 2, the same problem could happen. After the number of LTE autonomous denials reaches the configured limit, the UE will not be allowed to autonomously deny LTE UL during the remaining period. So if there is another unexpected significant ISM signaling that needs to be received during the remaining period, UE can't receive it because using autonomous denial of an LTE UL transmission is not possible, and then this significant ISM signaling will be missing which may cause big performance loss on ISM side, such as connection loss.
Since inherent to those mechanisms or solutions there are still issues to be solved, irrespective of the pre-existing proposals outlined above, there is still a need to further improve such systems.